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ACTINOCRINID.&. 617 
and 1 plate. Ventral disk conical, almost as high as the dorsal cup; grad- 
ually passing into the anal tube. The plates of the disk grow smaller as 
they approach the arm bases; the orals and radial dome plates larger and 
strongly nodose; the intervening smaller ones slightly tumid. Anal tube 
stout and long, extending considerably above the tips of the arms, and com- 
posed of small, tumid plates. The jomts of the stem vary considerably in 
width; some of the nodal joints in the upper part are nearly three times as 
wide as the internodals, and are provided with knife-like edges, while the 
edges of the internodals are but very little convex. 
Horizon and Locality. — Lower Burlington limestone ; Burlington, Iowa. 
Types in the collection of Wachsmuth and Springer. 
Cactocrinus multibrachiatus Hatt. 
Plate LVI. Fig. 6 and 7, and Plate LVIIL Fig: 8. 
1858. Actinocrinus multibrachiatus — HatL; Geol. Rep. lowa, Vol. I., Part IL., p. 580, Plate 10, Fig. 10. 
1881. Actinocrinus multibrachiatus — W. and Sp.; Revision Paleocr., Part IT., p. 144. 
Syn. Actinocrinus multibrachiatus var. echinatus Hau; Descr. New Spec. Crin., p. 10. 
Calyx gradually and evenly spreading to the bases of the free arms, dis- 
tinctly truncated at the lower end, and slightly depressed between the rays 
at the arm regions. The ventral disk fully one third lower than the dorsal 
cup, and surmounted by a moderately large, almost central tube. Plates of 
the dorsal cup all marked by strong radiating ridges proceeding to the sides 
of the plates, and meeting in the centre, where they form a conspicuous 
angular node, which is transverse upon the radials and costals. The ridges 
passing up and down the radials and brachials are more prominent than any 
of those proceeding to, or coming from, the interbrachials. Between the 
radials and basals there are three such ridges, or four where the former rest 
upon two basals, while the other plates have but one to each side. 
Basals short, their lower margins projecting outward, forming a sharp rim, 
which extends beyond the sides of the column, and is deeply notched at the 
sutures. Radials nearly as long as wide. First costals one third smaller than 
the radials, three of them hexangular, the two posterior ones generally 
pentangular; second costals a little smaller than the first. Distichals still 
smaller, and all axillary ; the outer ones supporting an arm, which is free 
from the second or third plate ; the inner ones two palmars, of which again 
the inner one in both divisions of the ray is axillary, and supports two arms; 
the outer one is truncated, and followed by one arm; all arm-bearing plates 
78 7 
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